Weighing scale



April 18, 1961 F. E. GOLDING 24,969

' WEIGHING SCALE Original Filed Sept. 20. 1956 IN V EN TOR.

FRfiA/K E 60L D/A/G g m? A TTUR/VEYS United States PatentO WEIGHIN G SCALE Frank E. Golding, Toledo, Ohio, assignor, by mesne assignments, to Toledo Scale Corporation, Toledo, Ohio, a corporation of Ohio 4 Claims. (Cl. 177-200) Matter enclosed in heavy brackets appears in the original patent but forms no part of this reissue specification; matter printed in italics indicates the additions made by reissue.

This invention relates to weighing ular to parts counting scales.

The principal object of this invention is the provision of an electrical parts counting scale.

Another object of the invention is to combine weighing and parts counting functions in a single electrical apparatus. v

A further object is to provide, in the electrical parts counting scale, means for selectively increasing the capacity of the scale.

Still another object is to facilitate the accurate adjustment of the electrical parts counting scale.

Other objects and advantages will be apparent from the following description of a preferred form of the invention.

scales and in partic- According to the invention, weighing and parts count ing functions are combined in a singleelectrical apparatus which comprises a pair of strain gage load cells or their equivalents, one cell for weighing a known number of sample articles and the other cell for weighing an unknown number of articles. The output voltages-of the strain gages, which are functions of loads applied to the respective load cells, cause a servo balance potentiometer slider to be positioned according to the ratio between the output voltages. An indication of such ratio in terms of the number of the previously unknown number of articles is made by an indicator that is automatically positioned according to the position ofv the potentiometer slider. Alternatively, one of the pair of strain gage load cells may be used for conventional weighing by efiecting an unbalance of a balanceable network in accordance with variations in a variable condition, 'i.e'.,

load upon the load cell, and causing a servo balance po tentiometer to operate as a result of such unbalance and return the network to a balanced condition. Provision also is made for meaus'to facilitate accurate adjustment of the apparatus and for means to selectively increase the capacity of the apparatus.

A. preferred embodiment of the invention is illustrated in the accompanying drawings. In the drawing:

Figure I is a schematic wiring diagram showing the essential components ofv the electrical weighing and parts counting scale.

Figure H is a simplified schematic wiring diagram which illustrates the basic operation of the parts counting function of the scale shown in Figure I. I

These specific figures and the accompanying description are intended merely to illustrate the inventiontand not to impose limitations on the claims.

, -.Reierring to Figure I, an electrical scale ments 5 in the other two legs. The bridges 3 are of an ordinary type used in gages available for measuring strain wherein the elements 4 and 5 are adapted to change in resistance with changes in a condition to be measured, e.g., loads applied to the load cells 1 and 2. It is to be appreciated, however, that other forms of electrical translators or transducers which produce electrical signals that are functions of the loads applied to [the] load [cells 1 and 2] receiver's may be used in place of the strain gage bridges 3. The bridges 3 or other load sensing combinations are energized by separate isolated secondaries 6 and 7 of a power transformer 8. The voltages or output'potentials derived from the bridges 3, which voltages are proportional to the weights of loads applied to the respective load cells, are applied to several scale circuits through output leads 9 and '10, the bridges being interconnected through a lead 11.

In order that measurements of loads applied to the load cells 1 and 2 may be obtained, the output leads 9 and 10 are connected through the scale circuits to a constant resistance 12 and to a sliding contact 13, respectively, of a servo balance potentiometer 14 which, when the apparatus is conditioned to be used as a parts counting scale, is excited by the output potential of the sample load cell 1. A tare adjust potentiometer 15, an amplifier and motor control device 16, a quadrature adjust potentiometer 17, and a zero adjust potentiometer 18 are connected in circuit with the output lead 10. The amplifier and motor control device 16 functions to control the operation of a motor 19 which both positions an indicator 20 and the sliding contact 13 of the servo balance potentiometer 14 through a mechanical connection 21. A span adjust variable resistor 22, which functions to adjust the voltage across the potentiometer 14, is connected in circuit with'the output lead 9. The potentiometers 15, 17 and 18 and the variable resistor 22 have sliding contacts 23,- 24, 25 and 26, respectively, which are adapted to be positioned manually. Separate isolated secondaries 27, 28 and 29 function to energize the potentiometers 15, 18 and 17, respectively.

When the apparatus is conditioned to be used as a parts counting scale, as hereinbefore mentioned, the servo balance potentiometer 14 is excited by the output potential of the sample load cell 1, the output lead 9 of the load cell 1 being connected to the constant resistance 12 of the potentiometer 14 through a switch 30 which is positioned for the parts counting operation as illustrated I in Figure I.

bpthjweighing and parts counting ,operationsin'cludes 'a.

sample load cell or receiverl and a counting load cell or receiver 2.1 f conventional type... Bachof thecells 1 and; wire strainbridge shaving'w' 22 comprises a'resista r eems t a is a d The bridges 3 of the load cells 1 and 2 are balanceable networks that are adapted to be unbalanced in response to changes in loads applied to the load cells. The output potential of the load cell 2 opposes the output potential of the servo balance potentiometer 14 which is excited by the output potential of the load cell 1, the potentiometer 14 driven by the motor 19 serving as a continuously automatically adjustable voltage source or alterable signal souce. The output potential of the load cell 2 opposes the output voltage or signal from the servo balance potentiometer circuit connected thereto to determine the flow of curent through the amplifier and motor control device 16. An unbalance oftheoutput .voltages from the load cell 2 and from the potentiometer 14 results in operation of the motor 19 to position the indicator 20 and the contact 13 of the potentiometer 14 until the opposing voltages are equal whereby input voltage to the amplifier 16 is restored to null, i.e., the signal from the potentiometer 14 is altered automatically to a level balancingthe output potential of the'counting load cell 2. i

The sliding contact 13 is connected through a-lead 31 the zero adjust potentiometer lfl-ofa 'zero compensaf a uon transformer 28 and a voltage divider thereacross having the sliding contact 2S whose'position can be altered. The function of this circuit is to insert a zero compensation voltage which in cooperation with the. circuit next to bediscussed results in positioning the indicator 20 at zeroindication on an indicia bearing chart 32 when no load is upon the scale. This function is realized by altering the position of the sliding contact 25.

The zero compensation circuit is connected through a lead 33 extending from the sliding con-tact 25 to the quadrature adjust potentiometer 17 of a quadrature signal oompensating circuit connected across the secondary; 29 of the transformer 8. This circuit comprises a condenser 34 and; a tapped resistance 35 of such magnitude with respect to the condenser reactance at the operating frequency that the voltage between the lead 33 and the sliding contact 24 on the resistance 35 is essentially in quadrature with the zero compensation voltage. The magnitude of thissuperimposed quadrature component is established by appropriate positioning of the sliding contact 24 whereby the quadrature components in the difference voltage are cancelled as is well understood in the art.

The output lead from the counting load cell 2 is connected to the tare adjust potentiometer of a circuit comprising the transformer secondary 27 of the transformer 8 and a votlage divider thereacross made up of a fixed resistance 36, a tare calibration variable resistor 37, and. a resistance 38 having the sliding contact 23 whose position can be altered. The function of this circuit is to introduce a voltage which has a 180 phase relationship with the load cell output for adjusting the scale indicator to zero. indication, on the chart 32 even though: tare weight, such; as ,a container for an unknown quantity of articles or parts, is. upon; the load cell 2. This function is realized by altering the position ofthe sliding contact 23 which is calibrated in pounds.

The basic operation of the parts counting function-of. the apparatus may be shown in mathematical terms with reference to Figure II as follows:

and, sliding contact13 P' M ES K1II1K1V therefore: a is proportional to N.

the sliding contact 13, since m'is a known number,'and since a is proportionalto N, the chart 32 may be calibrated to indicate Nm, the number of the previously unknown number of articles upon the counting load cell 2. In other words, the sliding contact 13 of the servo balance potenti- I Since the scale indicator 20 is mechanically connected to ometer 14 is positioned according to'thej ratiobetwe'en'the,

output potentials of the load cells 1 and 2 and indicator.- 20 which is coupled, to the sliding contact 13;fu.r1etit $ns;to indicate on the calibrated chart 32 :suchratio in terms of the number of the previously unknown number of articles:-

uponthe counting load' celll. 1

4 articles to be counted is placed upon the sample load cell 1. For example, two, five, or ten parts may be used, depending on the weight of the individual parts. If the sample load cell 1, for example, has a five pounds capacity, the total weight of the sample quantity must not exceed five pounds, but the greatest allowable sample should be used. It is to be appreciated that any convenient sample of parts may be chosen, the numbers two, five and ten being selected at random for the purpose of the present explanation. Since the numbers, two, five and ten have been chosen, the chart 32 is calibrated in three rows 39, 40 and 41, the inner row 39 being used for a sample of two, the middle row 40 being used for a sample of five, and the outer row 41 being used for a sample of ten, as indicated in Figure I. In other words, the chart 32 has a calibrated scale for each possible sample quantity. The operator must use the appropriate calibration. If desired, mechanical means for exposing only one calibrated scale at a time may be provided. The weight of the container for the unknown quantity of parts, which weight must have been determined previously, is set into the system by adjusting the sliding contact 23 of the tare adjust potentiometer 15 which is calibrated in pounds, the container of parts being placed upon the counting load cell 2.

Indicia in the inner row 39 on the chart 32 are read clockwise from 0 to 200, indicia in the middle row 40 are read clockwise fromO to 500, and indicia in the outer row 41 are read clockwise from 0 to 1000. It is often desirable to expand the capacity of the chart 32 and this is accomplished by exciting a voltage divider 42 which has taps 43, 44 and 45 to give 1 to l, 10 to l, and to 1 ratios, respectively. A fixed. resistor 46 is connected in series to. lower the maximum output potential of the counting load cell 2 to alevel, slightly below the maximum output of the sample load cell 1. A selector switch 47 connects the desired tap of the voltage, divider 42 to the amplifier 16 and functions to-selectively reduce the output potential of the counting load cell 2 by a ratio factor to increase the capacity of the scale. a

The unknown number of articles or parts in a container uponthe counting load cell 2 is determined by multiplying the chart indication by one of the three ratio factors.

For example, using a sample of two upon the sample load cell 1 and a ratio of 100 to 1, 20,000 parts in a container upon the counting loadcell 2 can be counted by multiplying the chart indication 200 by 100, or using a sample of five, upon the sample load cell 1 and a ratio of 10 to 1,. 5,000 parts in a container upon the counting load cell 2 ,can be counted by multiplying the chart indication of 500 by 10, or using a sample of ten upon the sample load cell 1 and a ratio of'l to 1, 1000 parts in a container upon the counting load cell 2 can be counted by multiplying the chart indication of 1000 by l.

Theziapparatus is conditioned to make weight measurements instead of count measurements by switching the sample load'cell. 1 out of the circuit and by switching a calibrated excitation for the servo balance potentiometer 14 into the circuit. This is accomplished by moving the switch 30 from its position shown in Figure I to connect with a terminal 48 of an alternate means for exciting the potentiometer 14. Such means includes a secondary ,49 of. the transformer 8 and afixed resistance 50 and a variable resistor 51 in series therewith. Hence, the switch 30 functions-as means for. selectively connecting either the alternatemeans or the sampling load cell 1 to the servo balance potentiometer. 14 for exciting the potentiometer 14'. 1 v 1 When the apparatusis conditioned to make weight measurements, such measurements are indicated bythe ,indicator 20nwhich cooperates with a series of weight indicia 52'ontthe chart 32, the cha'rt 32 being calibrated foo 'conditionszwhich may'exist inithe-system whenthe- M11543.attireselectorswitch;47 is connected to-ithe ampliflerand motpr yeontrolf dewice"16. In practice,"tliei s. "is'calibrated by first altering zero "and quadrature compensation circuits with no load upon the load cell 2 to that condition which balances the amplifier input with the contact 13 near an end of the servo balance potentiometer 14 and the indicator 20 reading zero. A series of standard weights are then applied to the load cell 2 and the contact 26 on the resistor 22 altered so that the span of the scale is correct. Tare weight may be set into the system by adjusting the sliding contact 23 of the tare adjust potentiometer 15 as hereinbefore described in connection with the parts counting function of the apparatus.

In operation, a load is placed upon the load cell 2 which causes the bridge 3 of the load cell 2 to become unbalanced and to develop an output voltage which is a function of the load, i.e., the bridge 3 of the load cell 2 generates a signal proportional to the weight of the load applied to the load cell 2. Such output voltage opposes the output voltage of the servo balance potentiometer 14, the potentiometer 14 driven by the motor 19 serving as a continuously automatically adjustable voltage source, i.e., the potentiometer l4 driven by the motor 19 serves as means for generating a balancing signal. The output voltage of the strain gage bridge 3 opposes the output voltage of the servo balance potentiometer 14 connected thereto to determine the flow of current through the amplifier and motor control device 16. An unbalance of the output voltages results in operation of the motor to' position the indicator 20 and the contact 13 of the potentiometer 14 until the opposing voltages are equal, the indicator 20 indicating on the chart 32 the weight of the load upon the load cell 2.

Various modifications may be made in details without departing from the scope of the claims.

Having described the invention, I claim:

1. An electrical parts counting scale comprising, in combination, a pair of load cells, a first one of the load cells functioning to weigh a known number of sample articles and a second one of the load cells functioning to weight an unknown number of like articles to be counted and each having circuit means generating an output voltage proportional to the loading of the individual load cell, said output voltages opposing each other, servo means responsive to differences between said voltages for adjusting one of the output voltages to a level balancing the other one of the output voltages,.the servo means being positioned according to the ratio between said voltages, indicating means coupled to the servo means for indicating the ratio between said voltages in terms of the number of articles upon the second load cell, and means for selectively changing the output voltage of one of the load cells by a ratio factor to change the capacity of the scale, whereby the number of articles upon the second load cell is determined by multiplying the indication by the factor.

2. An electrical parts counting scale comprising, in combination, a pair of load cells, a first one of the load cells functioning to weigh any one of a plurality of known numbers of sample articlesand a second one of the load cells functioning to weigh an unknown number of like articles to be counted and each having circuit output voltages to a level balancing the other one of the output voltages, the servo means being positioned according to the ratio between said voltages, indicating means coupled to the servo means and having a calibrated scale for each one of said plurality of known numbers of sample articles for indicating the ratio between said voltages in terms of the number of articles upon the second load cell, and means for selectively changing the output voltage of one of the load cells by a ratio factor to change the capacity of the scale, whereby the number of articles upon the second load cell is determined by multiplying the indication by the factor.

means generating an output voltage proportional to the loading of the individual load cell, said output voltages opposing each other, servo means responsive to differences between said voltages for adjusting one of the 3. An electrical parts counting scale comprising, in combination, a pair of transducer means, a first one of the transducer means functioning to weigh a known number of sample articles and a second one of the transducer means functioning to weigh on unknown number of like articles to be counted and each having circuit means generating an output voltage which is a function of the loading of the individual transducer means, said output voltages opposing each other, operating means responsive to differences between said voltages for adjusting 'one of the output voltages to a level balancing the other one of the output voltages, the operating means being positioned according to the ratio between said voltages, indicating means coupled to the operating means for indicating the ratio between said voltages in terms of the number of articles upon the second transducer means, and means for selectively changing the output voltage of one of the transducer means by a ratio factor to change the capacity of the scale, whereby the number of articles upon the second transducer means is determined by multiplying the indication by the factor.

4. An electrical parts counting scale comprising, in combination, a pair of transducer means, a first one of the transducer means functioning to weigh any one of a plurality of known numbers of sample articles and a second one of the transducer means functioning to weigh on unknown number of like articles to be counted and each having circuit means generating an output voltage which is a function of the loading of the individual transducer means, said output voltages opposing each other, operating means responsive to difierences between said voltages for adjusting one of the output voltages to a level balancing the other one of the output voltages, the operating means being positioned according to the ratio between said voltages, indicating means coupled to the operating means and having a calibrated scale for each one of said plurality of known numbers of sample articles for indicating the ratio between said voltages interms of the number of articles upon the second transducer means, and means for selectively changing the output voltage of one of 'thetransducer means by a' References Cited in the file of this patent or the original patent UNITED STATES PATENTS 1,790,883 Thomas i Feb. 3, 1931 2,766,981 Lauler et al Oct. '16, 1956 2,767,974 Ballard et al Oct. 23, 1956 

